Retractable syringe with improved delivery efficiency and locking system

ABSTRACT

A plunger, a needle assembly and a retractable syringe comprising same are provided. The plunger comprises a plunger member and a plunger outer having a lock spring that prevents or impedes movement of the plunger member after needle retraction. The plunger further comprises another locking member for engaging the barrel to prevent or impede further movement of the plunger outer after delivery of fluid contents. The plunger member has a plunger seal which engages a retractable needle of the needle assembly for retraction. The retractable needle comprises a cannula and needle body with a plurality of fluid channels that co-operate with a fluid conduit of the plunger seal to efficiently direct fluid to the cannula. A needle retainer comprises a plurality of barbed arms releasably coupled to the needle body, whereby an ejector with tabs facilitates release of the retractable needle from the needle retainer to allow compressed spring-driven retraction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is the U.S. national stage of InternationalPatent Application No. PCT/AU2010/001677, filed Dec. 10, 2010 anddesignating the United States, which claims the benefit of U.S.Provisional Patent Application No. 61/289,259, filed Dec. 22, 2009,which are incorporated by reference.

FIELD

THIS INVENTION relates to syringes. More particularly, this inventionrelates to a retractable syringe that includes at least one lock toprevent re-use of the syringe and/or needle stick injury and/or providesmore efficient fluid delivery.

BACKGROUND

The practice of sharing syringes without adequate sterilization betweensuccessive users is a major contributor to the transfer of HumanImmunodeficiency Virus (HIV) and Hepatitis with subsequent severerepercussions for the sufferer and at a high cost to society forsupporting and providing medical attention to sufferers.

Furthermore, health professionals may be exposed to used syringes whichcan lead to inadvertent needle stick injuries and possible exposure toinfective pathogens or other contaminants.

In response to this problem, retractable syringes have been developedwith the aim of preventing syringe re-use and/or needle stick injury byused syringes.

SUMMARY

While retractable syringes have been developed with the aim ofpreventing syringe re-use and/or needle stick injury, there is still aneed to improve the safety and efficiency of retractable syringes whilekeeping manufacturing costs to a minimum, particularly for mass producedretractable syringes.

A preferred object of the invention is to provide a user friendly andsafe retractable syringe while keeping manufacturing costs to a minimum,thereby facilitating mass production and distribution of retractablesyringes.

Another preferred object of the invention is to provide a retractablesyringe which efficiently delivers fluid contents, thereby minimizingwastage of fluid contents.

Yet another preferred object of the invention is to provide one or morelocking systems to prevent or at least minimize syringe re-use and/orneedle stick injury.

In a first aspect, the invention provides a plunger for a retractablesyringe that comprises a barrel and a retractable needle, said plungercomprising a plunger member, a plunger outer and one or more lockingmembers.

Suitably, a first said locking member in use prevents or impedesmovement of said plunger member relative to said plunger outer and/orsaid barrel after needle retraction.

In one embodiment, the first locking member is a lock spring mounted tothe plunger outer.

In another embodiment, the plunger comprises a second locking member.Preferably, the plunger outer comprises the second locking member whichis capable of engaging the barrel. Suitably, the second locking memberis capable of engaging the barrel. at the end of injection of fluidcontents to thereby prevent or impede further movement of the plungerouter relative to the barrel.

Preferably, the plunger further comprises a biasing member, wherein theplunger member and plunger outer co-operate to releasably maintain saidbiasing member in an initially energized state.

Suitably, retraction of said retractable needle is facilitated by arelease of energy from said biasing member.

Non-limiting examples of biasing members include a spring, elastic orother device for storing releasable energy.

Preferably, the biasing member is a spring which is initiallycompressed.

In the context of the initially energized biasing member, or theinitially compressed spring, it will be appreciated that energizing ofthe basing member or compression of the spring is performed duringmanufacture of the plunger or retractable syringe (i.e before supply to,or purchase or operation by, the user).

In one embodiment, the plunger further comprises a retractableneedle-engaging member.

Preferably, the plunger further comprises a plunger seal.

In one embodiment, the plunger seal is mounted to the plunger member.

In one preferred embodiment, the plunger seal comprises said retractableneedle-engaging member.

In a particularly preferred embodiment, the plunger seal furthercomprises one or more fluid conduits.

The plunger may further comprise a control rod. Preferably, the controlrod is releasably connected to the plunger member. More preferably, thecontrol rod is frangibly connected to the plunger member.

In a second aspect, the invention provides a retractable syringecomprising a barrel; a retractable needle; and the plunger of the firstaspect.

In a third aspect, the invention provides a needle assembly comprising aretractable needle that comprises a cannula and a needle body comprisingone or more conduits that in use direct fluid to said cannula.

Preferably, in use the one or more conduits co-operate with one or morefluid channels of a plunger seal to direct fluid to said cannula.

Suitably, said needle body is engageable by a needle-engaging member ofa plunger.

Preferably, the needle assembly further comprises a needle retainerreleasably coupled to said needle body. In a preferred form, the needleretainer comprises a plurality of barbed arms that in use are releasablycoupled to said needle body. the needle retainer may comprise aplurality of centering bosses that facilitate self-centering of theneedle retainer during syringe assembly. The needle retainer maycomprise a plurality of guide channels which facilitate or guide theflow of glue or adhesive for adhering the needle retainer to the barrelduring syringe assembly.

Suitably, the needle assembly further comprises an ejector.

Suitably, the ejector facilitates release of the retractable needle fromthe retainer to facilitate retraction of said retractable needle whenengaged by said plunger.

In a preferred embodiment the ejector comprises a plurality of tabs thatreleasably engage said retractable needle.

Preferably, said tabs provide an acceptable or desired level ofretraction activation force for disengaging from the retractable needle.

Preferably, the needle assembly further comprises a needle seal.

In a fourth aspect, the invention provides a retractable syringecomprising a barrel and the needle assembly of the third aspect mountedthereto.

Preferably, said barrel further comprises a collar having one or morereleasing members that facilitate release of said controlling memberfrom said plunger outer.

Preferably, said syringe comprises a lock formed between said barrel orsaid collar and said plunger outer after injection of fluid contents ofsaid syringe.

Suitably, the syringe according to the aforementioned aspects is aprefilled syringe.

In this context, “prefilled” means that the retractable syringe containsdeliverable fluid contents before supply to, or purchase or operationby, the user. Accordingly, a prefilled syringe obviates the step of theuser filling the syringe with fluid contents.

According to the aforementioned aspects, typically, although notexclusively, the barrel is formed of glass.

In a fifth aspect, the invention provides a method of making aretractable syringe by assembling a plunger, needle assembly and/orbarrel according to any of the aforementioned aspects.

Suitably, the method includes the step of inserting a needle retainerinto a barrel of the retractable syringe, the needle retainer comprisinga plurality of centering bosses that facilitate self-centering of theneedle retainer in the barrel.

Preferably, the method includes the step of adhering the needle retainerto the barrel by providing a flow of adhesive through guide channels ofsaid needle retainer.

In a particularly preferred embodiment, the method of making theretractable syringe includes the sequential steps of:

-   -   (i) mounting a needle assembly as hereinbefore described to a        syringe barrel;    -   (ii) filling the barrel with fluid contents;    -   (iii) inserting a plunger seal into the barrel; and    -   (iv) coupling a plunger to the plunger seal.

Preferably, a collar comprising one or more releasing members is adheredto the barrel prior to step (ii).

In a sixth aspect, the invention provides a method of operating asyringe according to any of the aforementioned aspects.

Throughout this specification, unless otherwise indicated, “comprise”,“comprises” and “comprising” are used inclusively rather thanexclusively, so that a stated integer or group of integers may includeone or more other non-stated integers or groups of integers.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the invention are described herein withreference to the following drawings wherein:

FIG. 1 is a sectional view of an embodiment of a retractable syringe;

FIG. 2 is a sectional view of an embodiment of a plunger;

FIG. 3 is a sectional view of an embodiment of a plunger immediatelybefore the end of injection of fluid contents of a syringe;

FIG. 4 is a sectional view and a bottom view of an embodiment of aplunger seal;

FIG. 5 is a sectional view of an embodiment of a needle assembly;

FIG. 6 is a perspective view of an embodiment of a retractable needle;

FIG. 7 is a perspective view of an embodiment of an ejector;

FIG. 8 is a perspective view of an embodiment of a retainer;

FIG. 9 is a sectional view of an embodiment of a needle assemblyimmediately before retraction of a retractable needle;

FIG. 10 is a sectional view of an embodiment of a plunger immediatelybefore retraction;

FIG. 11 is a sectional view of an embodiment of a syringe duringretraction of a plunger and retractable needle engaged therewith; and

FIG. 12 is a sectional view of a lock formed between a barrel collar anda plunger outer after plunger retraction.

DETAILED DESCRIPTION

Referring to FIG. 1, an embodiment of retractable syringe 100 comprisesbarrel 110 having plunger end 114 and needle end 115. Barrel 110 ispreferably formed of glass. At plunger end 114 is located collar 113having a releasing member in the form of release ring 130. Collar 113may be mounted, glued, fitted or integrally formed with barrel 110. Inembodiments where barrel 110 is formed of glass, suitably collar 113 isglued or otherwise adhered to barrel 110. In embodiments where barrel110 is formed of plastic, collar 113 is preferably formed integrallywith barrel 110 (e.g by moulding). Release ring 130 may be mounted,adhered or otherwise fitted to barrel 110, or may be co-moulded withcollar 113 and barrel 110.

At needle end 115 of barrel 110 is mounted needle assembly 900comprising retractable needle 400 that comprises cannula 410 and needlebody 420, needle seal 430, ejector 600 and retainer 300. Typically,syringe 100 is supplied with removable protective cover 121 over cannula410.

Syringe 100 further comprises plunger 200 comprising plunger seal 800mounted thereto. Barrel 110 further comprises inside wall 118 which,together with needle seal 430 and plunger seal 800 define fluid space120 inside barrel 110. In a preferred embodiment, fluid space 120 isprefilled with fluid contents to be delivered by retractable syringe100.

Typically, barrel 110 is formed of glass. Preferably, retainer 300 isglued or otherwise adhered to inside wall 118 of barrel 110. In use,plunger 200 is movable axially into fluid space 120 to facilitatedelivery of fluid contents of retractable syringe 100.

Referring particularly to FIG. 2, FIG. 3 and FIG. 4, plunger 200comprises plunger member 210 comprising shaft 211, annular ledge 212 andseal-engaging member 216, which in this embodiment is screw threadedprojection 217, which engages complementary, screw-threaded recess 820of plunger seal 800 (see FIG. 4). In an alternative embodiment, sealengaging member 216 may be in the form of a snap lock projection thatengages a complementary recess in plunger seal 800. In either case, themale-female connection between plunger member 210 and plunger seal 800may readily be reversed so that the plunger member 210 has the femalemember and the plunger seal 800 has the male member.

Plunger member 210 further comprises locking groove 219, the function ofwhich will be described in more detail hereinafter.

Plunger 200 further comprises plunger outer 220 having elongate body 221with base 225 and head 222 in which is fitted cap 223. A first lockingmember comprises lock spring 224 mounted through slot 226 extendingthrough head 222 and cap 223 to thereby assist assembly of plunger 200.Typically, lock spring 224 is an “R-shape’ clip of stainless steelconstruction. Lock spring 224 and locking groove 219 co-operate to lockplunger member 210 and plunger outer 220 together at the end ofretraction, as will be described in more detail hereinafter withreference to FIG. 12. Lock spring 224 preferably provides up to 100Newton lockout resistance, which is a level of resistance desirable forsyringe 100.

Elongate body 221 further comprises a second locking member comprisinglocking finger 227 which has abutment 228. Engagement between lockingfinger 227 and release ring 130 of collar 113 will also be described inmore detail hereinafter with reference to FIG. 12.

Releasably, frangibly connected with plunger member 210 is control rod230 comprising button 231, arm 232 and shaft 233. Plunger 200 furthercomprises compressed spring 270 which is mounted between plunger member210 and plunger outer 220, held in an initially compressed state betweenannular ledge 212 of plunger member 210 and base 225 of plunger outer220. Button 231 may have a textured surface to improve feel and grip fora user.

As best shown in FIG. 3, control rod 230 is releasably coupled toplunger member 210 by way of shaft 233 which is releasably connected toplunger member 210 by frangible junction 234. Control rod 230 alsoreleasably engages plunger outer 220 to thereby retain spring 270 in aninitially compressed state held between annular ledge 212 of plungermember 210 and base 225 of plunger outer 220. Initially, ledge 235 ofarm 232 abuts rim 229 of head 222 of plunger outer 220 to thereby retaincontrol rod 230 and prevent axial movement of control rod 230 relativeto plunger outer 220. However, arm 232 of control rod 230 is resilientlyflexible and movable in the direction of the solid arrow shown in FIG.3, which will allow disengagement of control rod 230 from plunger outer220 to facilitate decompression of spring 270, as will be described indetail hereinafter.

Referring particularly to FIG. 4, plunger seal 800 is of unitaryconstruction and comprises seal body 840 and sealing ribs 850A, 850B,850C that effect a fluid-tight seal between plunger 200 and inside wall118 of barrel 110. Recess 820 of plunger seal 800 engages complementaryseal-engaging member 216 of plunger member 210 (see FIG. 9). In thisembodiment, recess 820 comprises a female screw thread 821 that engagesmale screw threaded projection 217 of plunger member. Plunger seal 800further comprises needle engaging member in the form of recessed seat810 that can receive segment 425 of retractable needle body 420. Plungerseal 800 also comprises recess 860 that receives fluid end 412 ofcannula 410 towards the end of plunger 200 depression, prior toretraction of retractable needle 400, as will be described hereinafter.In addition, recess 860 of plunger seal 800 comprises fluid conduit 826.

Needle assembly 900 is shown in more detail in FIG. 5, which comprisesretractable needle 400, retainer 300, needle seal 430 and ejector 600.These components are individually described with reference to FIGS. 6, 7and 8 respectively. Referring to FIG. 6, retractable needle 400comprises cannula 410 having delivery end 411 and fluid end 412.Retractable needle 400 further comprises needle body 420 which comprisesrespective body segments 421, 422, 423, 424 and 425. Body segment 425comprises fluid channels 426A, 426B. Needle body segment 424 comprisesshoulder 427 and needle body segment 422 comprises shoulder 428. In FIG.7, ejector 600 comprises ejector ring 610, bore 605 and respective basesegments 620A, B, C separated by slots 621A, B, C. Base segments 620A,B, C respectively comprise tabs 622A, B, C which as shown in FIG. 5,engage shoulder 427 of body segment 424 of needle body 420.

Referring to FIG. 8, retainer 300 comprises body 310 comprisingcircumferential groove 311, centering bosses 312, central aperture 313,rim 314 and guide channels 315, and further comprises arms 320A, 320B,respectively comprising hook-ends 321A, 321B. Circumferential groove 311and guide channels 315 create zones which facilitate or guide the flowof glue or adhesive for adhering retainer 300 to inside wall 118 ofbarrel 110. Centering bosses 312 have been included to overcome thepotential problem of centering retainer 300 in barrel 110 by providing aself-centering mechanism that simplifies centering of these componentsin high speed assembly and gluing machines, as would typically be usedfor the assembly of syringe 100. Centering bosses 312 allow contactbetween retainer 300 and barrel 110 at four separate points, withcomponents produced for all extremes of tolerance. The tolerancevariations between barrel 110 and retainer 300 are absorbed by thecrushing of centering bosses 312. In the absence of these structures, agap would be required between these components to allow for assembly atall tolerance extremes, which would require automated assembly machinesto have a system for centering the parts prior to gluing. Alternatively,centering would have to be performed by a mechanism external to, orotherwise separate from, the assembly machines. This would not bepractical for high speed assembly.

Referring again to FIG. 5, needle seal 430 comprises sealing base 431which seals against inside wall 118 of barrel 110 to prevent inadvertentleakage of fluid contents, body 432 comprising internal bore 433 andledge 434.

The sequence of events whereby retractable needle 400 is disengaged fromretainer 300 to facilitate retraction of retractable needle 400 is asfollows.

Typically, syringe 100 is provided prefilled with fluid contents fordelivery. Therefore, plunger 200 is provided in an initial positionready for depression to deliver the fluid contents of the syringe 100.During delivery of fluid contents, plunger 200 moves axially throughbarrel 110 in the direction of the hatched arrow in FIG. 9. Plunger seal800 bears against needle seal 430, which in turn bears against ejector600 thereby pushing tabs 622A, B, C of ejector 600 out of engagementwith needle body 420. In order to provide an acceptable or desired levelof retraction activation force, tabs 622A, B, C allow for tuning of theforce to disengage ejector 600 from needle body 420 by adjusting theheight of the tabs 622 until the push force required on needle seal 430to force ejector 600 out of engagement with shoulder 427 of needle body420 is at a level that is acceptable for use of syringe 100. The designof tabs 622A, B, C provides for simple machining of theinjection-moulding tool to provide the optimum engagement fit to provideacceptable disengagement.

Ledge 434 of needle seal 430 now rests on shoulder 427 of needle bodysegment 424. This facilitates moving needle seal 430 back up barrel withthe needle 400 on retraction (and serves as a stop for forward travel),Further to this, ejector ring 610 moves hook-ends 321A, B of arms 320A,B radially outwardly in the direction of the solid arrows in FIG. 9,thereby disengaging segment 422 of needle body 420 from retainer 300 torelease retractable needle 400 for subsequent retraction. At this point,recessed seat 810 of plunger seal 800 has engaged segment 425 ofretractable needle body 420 and recess 860 has received fluid end 412 ofcannula 410. This effectively couples retractable needle 400 to plungermember 210. Although not visible in FIG. 9, fluid channels 426A, 426B insegment 425 and fluid conduit 826 in recessed seat 810 in plunger seal800 assist in channeling residual fluid from within recessed seat 810into fluid end 412 of cannula 410. This minimizes “dead volume” (i.e avolume of undeliverable, hence wasted, fluid contents) and reduces thepossibility of a “hydraulic lock”, to thereby improve the efficiencywith which fluid contents of syringe 100 are delivered.

Referring to FIG. 10, plunger 200 moves axially in the direction of thehatched vertical arrow until the end of injection of fluid contents, atwhich time abutment 228 of locking finger 227 of plunger outer 220engages underside 131 of release ring 130 to thereby prevent movement ofplunger outer 220 out of barrel 110.

In order for retractable needle 400 to retract at the end of delivery offluid contents, compressed spring 270 must decompress, which isfacilitated by plunger member 210 disengaging from plunger outer 220.Again referring to FIG. 10, arm 232 of control rod 230 bears againstrelease ring 130 of collar 113 at plunger end 114 of barrel 110. Releasering 130 forces arm 232 to move radially inwardly n the direction of thehorizontal solid arrow and out of engagement with rim 229 of cap member223 of plunger outer 220 in FIG. 10. This disengagement allowscompressed spring 270 to decompress and push against ledge 212 ofplunger member 210 to thereby retract plunger member 210 with controlrod 230 coupled thereto, as shown in FIG. 11. This disengagement mayalso be accompanied by an audible and/or tactile signal (e.g. a “click”)which indicates to the user that retraction will occur. Retractableneedle 400 is coupled to plunger seal 800 and so retracts with plungermember 210 in the direction of the arrow in FIG. 11 inside barrel 110,thereby being completely enveloped by, and contained within, barrel 110.While retraction of needle 400 is “automatically” driven bydecompression of spring 270, the rate of retraction can be controlled bya user relaxing pressure (such as by way of thumb pressure) againstbutton 231 of control rod 230.

Referring to FIG. 12, at the end of retraction of plunger member 210,further movement of plunger member 210 relative to plunger outer 220and/or barrel 110 is prevented by lock spring 224 “snap locking” aroundlocking groove 219 in plunger member 210. The locking of plunger member210 at the end of retraction prevents inadvertent removal of plungermember 210 from plunger outer 220 and also prevents inadvertentdepression of plunger member 210, both of which would expose needle end411, and thereby expose the user to a potential needle stick injury.

At the end of retraction of plunger member 210 and retractable needle400, control rod 230 can be broken from plunger member 210 at frangiblejunction 234 and manually removed from retractable syringe 100 anddiscarded as “clean” waste so that there is little if any plunger 220protruding externally from barrel 110 with which to attempt to forceplunger 200 back into barrel 110 and attempt to re-engage the needle(not shown).

In light of the foregoing it will be appreciated that the presentinvention provides a relatively simple, robust and inexpensive syringethat is automatically disabled with little or no assistance from theuser to thereby prevent, or at least minimize the likelihood of, re-useof the syringe and/or needlestick injury by a used syringe.

More particularly, dual locking systems are provided whereby the plungerouter is locked to the barrel and the plunger member is locked to theplunger outer to thereby prevent removal and/or further movement of theplunger. Another particular advantage is provided by the lock springwhich can resist up to 100 Newtons force to prevent or impede furthermovement of the plunger member after retraction. By providing duallocking systems, inadvertent failure of one or the other lockingsystems, or overcoming one or the other locking systems throughtampering by an illicit user, does not result in the complete failure ofplunger lockout.

It will also be appreciated that the fluid conduits in the retractableneedle body and in the plunger seal provide more efficient delivery offluid contents timed to occur just before retraction of the needle. Incases where the fluid contents are an expensive drug or other compound,on a mass produced scale this improved efficiency can result inconsiderable cost savings. Furthermore, the retractable syringe retainerprovides a convenient “self-centering” system for mounting into thebarrel which greatly assists high speed syringe assembly. The guidechannels of the retainer also assist rapid, automated adhesion of theretainer in the barrel during syringe assembly.

Another advantage is provided by the ejector tabs described herein thatprovide an acceptable or desired level of retraction activation force.Adjustment of tab height allows for tuning of the force to disengage theejector from the retractable needle body, and hence the “push” forcerequired to force the ejector out of engagement with the retractableneedle body.

Throughout the specification, the aim has been to describe the preferredembodiments of the invention without limiting the invention to any oneembodiment or specific collection of features. Various changes andmodifications may be made to the embodiments described and illustratedwithout departing from the present invention.

The disclosure of each patent and scientific document, computer programand algorithm referred to in this specification is incorporated byreference in its entirety.

The invention claimed is:
 1. A plunger for a retractable syringecomprising a barrel and a retractable needle, said barrel having aninner wall, the retractable needle having a cannula extending through aneedle body, the needle body having one or more fluid channels, saidplunger comprising a plunger member that comprises a unitary plungerseal that comprises a needle-engaging recess and one or more fluidconduits in said needle-engaging recess that are capable of directingfluid to said one or more fluid channels in said retractable needle andwherein the unitary plunger seal seals against the inner wall of saidbarrel, a plunger outer and one or more locking members, a first of saidone or more locking members mounted to the plunger outer and capable ofpreventing or impeding further movement of said plunger member relativeto said plunger outer and/or said barrel after needle retraction.
 2. Theplunger of claim 1, which comprises a second of said one or more lockingmembers which is capable of engaging the barrel at the end of injectionof fluid contents to thereby prevent or impede further movement of theplunger outer relative to the barrel.
 3. The plunger of claim 1, whereinthe plunger further comprises a biasing member whereby the plungermember and the plunger outer co-operate to releasably maintain saidbiasing member in an initially energized state.
 4. The plunger of claim1, wherein the first of said one or more locking members comprises alock spring.
 5. The plunger of claim 4, wherein the first of said one ormore locking members is capable of engaging the plunger member afterneedle retraction to thereby prevent or impede further movement of saidplunger member relative to said plunger outer and/or said barrel.
 6. Aretractable syringe comprising a barrel, a plunger according to claim 1and a needle assembly.
 7. The retractable syringe of claim 6, which is aprefilled syringe.
 8. The retractable syringe of claim 6, furthercomprising a lock formed between the barrel and the plunger afterinjection of fluid contents of said syringe.
 9. The retractable syringeof claim 6 wherein the barrel comprises a collar.
 10. The retractablesyringe of claim 9, wherein the collar comprises one or more releasingmembers.
 11. The retractable syringe of claim 10, wherein the one ormore releasing members are in the form of, or comprise, a release ringoperable to disengage said plunger member from said plunger outer toallow decompression of said biasing means.
 12. The retractable syringeof claim 6 wherein the needle assembly comprises a retractable needlehaving a cannula and a needle body that comprises a plurality ofsegments, wherein a segment engaged by the needle engaging recess of theplunger seal comprises one or more fluid channels that in use cooperatewith the one or more fluid conduits in the needle-engaging recess of theplunger seal to direct fluid to said cannula.
 13. The retractablesyringe of claim 12, wherein the needle body is engageable by theneedle-engaging recess of a plunger to facilitate retraction of saidretractable needle.
 14. The retractable syringe of claim 12, whichfurther comprises a needle seal.
 15. The retractable syringe of claim12, further comprising a needle retainer releasably coupled to saidneedle body.
 16. The retractable syringe of claim 15, wherein the needleretainer comprises a plurality of barbed arms that in use are releasablycoupled to said needle body.
 17. The retractable syringe of claim 15,wherein the needle retainer comprises a plurality of centering bossesthat facilitate self-centering of the needle retainer during syringeassembly.
 18. The retractable syringe of claim 15, wherein the needleretainer comprises a plurality of guide channels which facilitate orguide the flow of glue or adhesive for adhering the needle retainer tothe barrel during syringe assembly.
 19. The retractable syringe of claim12, further comprising an ejector.
 20. The retractable syringe of claim19, wherein the ejector facilitates release of the retractable needlefrom the needle retainer to allow retraction of said retractable needlewhen engaged by said plunger.
 21. The retractable syringe of claim 19,wherein the ejector comprises a plurality of tabs that releasably engagesaid retractable needle.
 22. The retractable syringe of claim 21,wherein said tabs provide an acceptable or desired level of retractionactivation force for disengaging the retractable needle.
 23. A method ofmaking a retractable syringe including the step of inserting a needleretainer into a barrel of the retractable syringe, the needle retainercomprising a plurality of centering bosses that facilitateself-centering of the needle retainer in the barrel, providing aretractable needle having a cannula extending through a needle body, theneedle body having one or more fluid channels, inserting the retractableneedle into the barrel, providing a plunger including a plunger outer,one or more locking members, and a plunger member, the plunger memberincluding a unitary plunger seal that includes a needle-engaging recessand one or more fluid conduits in said needle-engaging recess that arecapable of directing fluid to said one or more fluid channels in saidretractable needle, a first of said one or more locking members beingmounted to the plunger outer and capable of preventing or impedingfurther movement of said plunger member relative to said plunger outerand/or said barrel after needle retraction, and inserting at least aportion of the plunger into the barrel so that the unitary plunger sealseals against an inner wall of said barrel.